Electrical instrument for diagnosing and assisting defective hearing



March 18, 1930." B. LANGENBECK AL 1,750,960

ELECTRICAL INSTRUMENT FOR DIAGNOSING AND ASSISTING' DEFECTIVE HEARING Filed July :51, 1928 I l U l l I l l I I a I I l l l I l I I I l l I 1:11 ye nTo rs .Perrvfiamllayeakf Patented Mar. 18, 1930s,

' UNITED STATES IBERNHABD i'JANGENBECK, F LEIIPZIG, AND

GERMANY, ASSIGNORS T0 SIEMENS 8'0 HALSKE .AKTIENGESELLSCHAFT, STADT, NEAR BERLIN, A. CORPORATION OF GERMANY PATENT OFFICE HELDZUT SELL; OF IBEBLIN-SIEMENSSTADT,

OF SIEMENS- ELECTRICAL INSTRUMENT r03 DIAGNOSING. Aim ASSISTING DEFECTIVE HEARING Application filed July a1, 1928, Serial No.

Our invention relates to electrical instruments for diagnosing and assisting defective hearing".

Sound amplifying instruments for the use of persons afflicted with defective hearing do not operate satisfactorily at an amplification above a certain limit, even if the usual mistake of using the lower acoustic frequencies is avoided,-and this is particularly the case with electrical instruments of this type, which amplify the audible sounds practically uniformly over the whole range of frequency, as a limit is soon reached, above which the amplification can not be raised because, al-

though the instruments may work physically in a perfect manner, speech becomes unintelligible, or at least reaches the ear in such a distorted manner, that the attention of the person with the defective hearing is strained to an excessive amount, and he becomes tired out very quickly.

This phenomenon is connected with the fact that in human speech sounds of low frequency possess great energy but are not especially important for understanding whereas the sounds of high frequency, for instance within a frequency range from 1000 to 4000 cycles per second are not so sonorous, but are of the greatest importance for the,

understanding of speech.

At a certain amplification, which is assumed to be uniform for all audible frequencies, the sounds of lowfrequencies, in themselves already strong, are brought to the earv in far too great a volume. v

This very often causes pain in the middle ear, and subjective combinations and overtones are induced in the car which confuse and distort the speech, and thereby make it unintelligible, in consequence of the overloading due to the fact that the intensity of the sounds perceived by the earis not direct- 1y proportional to those emitted by the sound conducting apparatus. The sounds of. higher frequencies are obscured by the low sounds, they are completelysubmerged, and just because the high frequency components are essential for a clear understandigg, the speech becomes quite unintelligible. 50 must be added the noises in the room and 0 this 296,557, and in Germany April 12, 1927.

before or during their" amplification by means of the electrical device for assisting defective hearing), such choking or throttling efi'ect starting at av certain frequency, and this effect is increasingly greater as the sound frequency is lower, it being possible to choose arbitrarily, within certain limits the frequency at which the throttling starts. The intensity of the throttling effect may also be aljusted toward the lower sounds, as desire This throttling, depending on the frequen- I cy, which could be effected in any suitable manner, for instance by acoustic means, is preferably effected by electric means, that is through an aperiodicchain of filters, which are placed in circuit behind thesound receiving microphone and in front of,- or under.

. certain conditions, in the electric amplifying device. In consequence of thethrottling effect increasing at the lower frequencies, the

sounds 'of lower frequencies are only slightl increased, and the ear will not be straine The sounds of the high frequencies, especially the essential components are no more submerged, in fact they become slightly overdistinct, so that the speech can be easily understood.

- The above mentioned disadvantages of a uniform sound amplification over all audible frequencies, and the advantages of a throttling effect according to the invention .are especially pronounced in the case ofso called nervous deafness in which the hearing is especially defective in the higher notes.- The new, preferably electric instrument may be used not only as a hearingappliance for the deaf, but also for diagnosing defective hearing, in a manner similar to that in which a set of spectacles is used for sight testing, that is the throttling can be variably adjusted so as to find out the adjustment most favorable for intelligible speech. The invention will now be described with I reference to the accompanying drawings.

' throttling"eflie ct for the". I

stants but; through a chain of twoi nembersi curves can however be rounded ofi-by nces and capacities for" Figure I the assembly of anelectric instrument according to the invention is shown diagrammaticall Figure 2 shows a chain of filters adapted 3 to be put in circuit between the sound receiving microphone and an electrical amplifying device,

Figure 3 shows curves explaining the working of the chain of filters. 1

Figure 4 is 'a diagram'illustrating the operation of the filter chain under different con-- ditions. 1 v

In Figure 1 m denotes the soundreceiving instrument, which comes into satisfactory operation with sounds of the highest frequency which are important Ito the intelligibility of speechyor if desired reproduces these sounds in preference; a

- The speech currents are led to an aperiodic v filter s the circuit and preferred electrical dimensions o'f-which. are shown in "Figure 2.

" The filter comprises a plurality of condensers (for instance 1 microfarad, and 1/10, 1/100, and 1/ 1000 of a micr and respectively) con- 2 nected in series, whi e in each of the members 1, 2, 3, 4, of the filter chain a shunt resistance is provided (for instance of 200, 2,000, 20,000

. and 200,000 ohms respectively). Any desired number of chain members may be switched in orout by means of suitable switches (not shown). The tension taken from the filter 8, depending on the frequency,

is led to an amplifying deviceV which feeds.

a telephone 2? which is preferably made especially sensitive to the high'sounds and is v well damped.

The several capacities and resistances can I be so chosen, that the throttling efi'ect. starts at a predetermined frequency, and the throt- 40 tling eflect can be increased at will in'relahow the increase of the throttling degrids atdeereasing irequency, upon the mm 0t a ed Show; the

chain members.- I The full line an" tll throttling, eficct "through-"a chain consisting Y oi aone-membefi chairi'f two difierent time 1constants,jth e' dot and show the choosing other resista m "both.chain members. v

' If a valve circuit is used for am lification 0f the ch currents, wherein:

- and capacities; their t'h'e .embodiment i-1.81m; in Figure 51; wherein magma 5 "members of the filter 'ure 2.

curves of Figur "sarily be designed according to Figure 2, but

igure 3, where 1. In an electricalinstrument for acoustic same twotime con- 1,75o,eeo,

ters 8, arranged separately from the amplifying device V, can be combined with-the valve amplifier. The several valves are in the case of the so called resistance amplifier connected together by .means ofgindividual 6 chain'members which are inprinciple designed in'the same way as the individual chain, shown in Fig- Instead of dimensioning, as .is usual, the capacities and resistances in such a manner that a practically uniform amplification results over the whole requency range of the audible sounds, they are so chosen, accord ing to the invention, that a-throttling efiect results in the manner. represented by the o3. The members of the filter need not necesmay for instance also contain-self-inductances, but so connected and of such dimensions that the individual members do notconstitute a slightly damped oscillating circuit, as these might be excited to oscillation by the several sounds of the speech to be amplified, and the equalizing process might have a deleterio s effect on the intelligibility of the spec transmission. 7 Y The diagram Fig. 4 illustrates the relationship between the pitch of the sounds (ab.- scissae) and the ratio (ordinates) between outputvoltage and input voltage, for several dilferent circuit arrangements of the filter chain. Curve a shows the condition obtaining when only the first member 1, of the chain is included in the circuit, curve I) illustrates the condition-resulting upon the inclusion'of both chain members 1- and 2 in the circuit,

curve '0 shows 'tliecondit'ion obtaining when the three'chainmembers 1, 2, and 3 are ineluded in the circuit, and curve d illustrates the condition resulting upon the inclusion of all four chain members 1, 2, 3, and 4 in the circuit.

It is of course evident that 'all other parts of the device, suchas the receiving micro- I phone and the telephone, must be'damped as much as possible. i

We claim: a

urposes, one or more aperiodic filterf memrs which consist-of condensers in the mam circuit and of resistances in the coupled branch circuits and which are so dnnen-' sioned that theyv ,attentuate the sounds of'12 lower fr uencyi, and a receiving microphone,

whicl'nin epen entlyof thethrottling trans missionlarra'ngement, selects the'sounds of high frequency. for'reproduction'.

2. In an electrical instrument for acoustic f one or more aperiodic filter mem- 7 several, valves. are coupled wit resist-- rs which consistof condensers in the main circuit: and of resistances in the. coupled quency, and a receiving microphone, which, independently of the throttling transmission arrangement, selects the sounds of high frequency for reproduction, and a high tuned and especially well damped telephone.

3. In an electrical instrument for acoustic purposes, one or more aperiodic filter members employed as a coupling between the amplifying valves of a resistance amplifying circuit which consists of condensers in the main circuit and of resistances in the coupled branch circuits, and which are so dimensioned that they attenuate the sounds of lower frequency. 4. An electrical instrument for acoustic purposes, comprising a transmitter, an adjustable electrical device, which throttles the audible sounds from a predetermined limit frequency in a ratio increasing towards low frequencies, and a receiver to translate the electrical waves into sound waves.

5. An electrical instrument for acoustic purposes, comprising a transmitter, an adjustable electrical throttling device operating as an aperiodic filter and consisting of condensers in'the main circuit and of resistances in the coupled branch circuits, dimensioned to attenuatethe sounds of lower frequency, and a receiver to translatethe electri cal waves into sound waves.

In testimony whereof we affix our signatures.

BERNHARD LANGENBECK. HELMUT SELL. 

